Means for grinding material



Dec. 11, 1945. F. SWENSON ETAL 2,390,967

MEANS FOR GRINDING MATERIAL 2 Sheets-Sheet 1 Filed Jan. 5, 1942 [rll' WlummlllHmiT q; I 5 g 5 Q";

INVENTORS @ZZJW (5 494 v-M A Mw I Dem 11, 1945. I swE so ETAL 2,390,967

MEANS FOR GRINDING MATERIAL Filed Jan. 5, 1942 2 Sheets-Sheet 2 IN VENT ORS 6444/ 4) (LL/rm Patented Dec. 11, 1945 MEANS FOR GRINDING MATERIAL Frank Swenson and Erik Iver Erikson, Weatherly, Pa., assignors to Linotype Parts Company, Weatherly, Pa., a partnership Application January 5, 1942, Serial No. 425,584

8 Claims.

This invention relates to grinder and dressing mechanisms adapted for reducing the work to be ground to within very close limits.

, It is especially related to mechanism adapted for grinding flat surfaces, such as highly perfected surface grinding machines found on the market, operating each in conjunction with a suitable dressing device for truing and cleaning the active surface of the emery wheel or other grinding wheel.

Where accuracy in grinding operations is required to within a small fraction of one-thousandth of an inch it is essential that before making the final or finish grind on a piece of work, the surface of the grinding wheel be newly dressed whereby to eliminate from this surface the fine chips of ground material which have entered into and are embedded in the abrasive material. Dressing the surface will not alone assure a clean surface on'the work, but also permit the operator to obtain an accuracy extending to within the close limits above referred to.

In order to do this type-of work the common procedure has been to first grind the work to a size requiring only a fraction of one-thousandth of an inch for a finishing grind. Before dressing the wheel for a. final cut the operator will therefore leave the work, say one half of onethousandth of an inch heavier, as indicated by the graduation on the machines hand wheel, adapted to raise or lower the grinding wheel. He then moves the dressing device, located on the table of the grinding machine, toward the grinding wheel and lowers the latter in order to have its surface touch the cutting or diamond point of the dressing device. The operator will now remove from the grinding wheel a definite amount of its material and thereby reduce its radius, the exact amount thereof he is however unable to determine within a fraction of one-thousandth of an inch. Even though the machines graduated hand wheel will give an approximate'indication how far he has lowered the grinding wheels surface away from the surface of the work, the amount of material however which he has removed from the grinding wheel is undetermined for the reason that the operator cannot ascertain how far the diamond point enters the grinding wheels surface when first causing the point only to touch the same.

It is humanly impossible to determine whether this touch is within a fraction of a thousandth of an inch and it is consequently not possible to accurately determine, b means of the graduated hand wheel, how to re-set the grinding wheel in relation to the Work in order to get the required dimension for finish grind on its surface.

The operator is therefore obliged to first make one more grind operation for the purpose of measuring the work. Having ground the work,

he will remove and measure it. After replacing same on the machine and knowing how much more to take off, he will now set the handwheel and grind the work to finish size.

It is obvious that the method employed is to be repeated over and over again under conditions where, when quantity production is concerned, considerable time is to be expended in turning out a large amount of such work.

To save time in production more grinding-machines and consequently more operators for these machines are required.

It is therefore one of the main objects of this invention to provide a meanswher'eby the operator, after having set thetgrinding machine and having determined on the graduatedadjustment handwheel the desired height of the grinding wheel in relation to the finished size of the work, will be in a position to continuously grind in successive operation for production purposes, quantities of identical or similar parts to substan tiall equal thickness varying within less than one-thousandth of an inch, without requiring the operator to remove the work fromthe machine and measure the work before making the final grind operation. v

It is a. further object of this invention to provide a dressing device of which the height movement at its rotatable diamond point can be controlled in a definite manner.

Another object of this invention is to provide the height controlling mechanism of said dressing device with graduations for measuring its length of movement.

A further object of this invention is to provide said height controlling mechanism with graduations of which their magnitudes are equivalent to those marked on the grinding machines handwheel for raising and lowering the grinding wheel, whereby both sets of graduations may operate in direct relation to each other.

These and. other objects which will be pointed out more specifically in the specification and the claims, are attained by the invention disclosed in the drawings, wherein,

Fig. 1 is a front elevational view of a grinding machine in combination with a dressing device.

Fig, 2 is a sectional side view of a new type dressing device.

Fig. 3 shows perspective view of blocks for said dressing device.

Referring to the drawings, the surface grinder l of any suitable manufacture found. on the. market, has a table, 2 which is adapted to travel longitudinally toward and from the grinding wheel 3 and be operated by a hand wheel 4. A second hand wheel 5, which is to the right of wheel 4 is for the purpose of moving the table crosswise, whereby to enable the operator to dress the surface of the grinding wheel 3 by means of a. dressing tool 6, attached or held to the table 2.

The grinding wheel is vertically movable on a rigid slide. Its up and down movement is controlled by a handwheel I which has a graduated rim 8.

The graduations thereon are spaced sufficiently wide for the operator to accurately determine the grinding wheels vertical movement substantially to within two ten-thousandths of an inch.

Table 2 is provided with a conventional type magnetic chuck 9 which is holding to its upper surface the work I to be ground to the height or thickness required.

Referring to applicant's truing device or tool 6, shown in Figs. 1 and 2, the diamond holder with its diamond point 2| at its upper end, is rigidly held by means of a clamping screw 22, in an adjustable sliding member 23 movable longitudinally in an angular displaced frame 24, comprising a rigid sleeve 25 having integral therewith a mounting plate 26, adapted for securing same to a supporting block 21 which in turn is fastened to a table bracket 28 held by suitable bolts 29 to the table 2 of the surface grinder.

Slidingmember 23 is guided in sleeve 25 and prevented from rotating by means of a screw 3| entering a slot 32 in member 23. Screw 3| also serves to lock the sliding member while the diamond point is operating.

Th lower end of member 23 is provided with a left-hand threaded hole into which enters a mi crometer screw 33 provided with a flange 34 and anextension in form of a shank 35. To the end part of this shank is fastened a knurled knob 36 having a clear circular surface provided with graduations-3'l adapted for indicating magnitudes of one-thousandth of an inch and fractions thereof and within which limits the diamond point may be raised or lowered. Due to the angular displacement of the axis of the diamond holder and the micrometer screw 33 the pitch of the screws thread has been selected in definite relation with the angle of the axis, whereby to conform with the graduated decimal inch values when turning the knob 36. Both shank and its flange 34, are guidedin a cap 38 screwed against the end part 39 of sleeve 25 in a manner to enable flange 34 to freely rotate between the inner surface 40 'of cap 38 and the end surface 4| of end part 39.' l

The lower angular surface of cap 38 is provided with a zero mark as shown in Fig. 1.-

Becausethe work l0 onthe magnetic chuck differs in thickness, depending on theparticular parts to be ground and because it is a characteristic of the present invention to have the height of the diamond point correspond to the finished height or thickness of the parts to be ground, it is essential that means are to be provided which will enable the operator to set the diamond point to that particular height determined by the work to be ground. For this reason any suitable number of blocks 21a, 21b, 21c, of different heights are made available to the operator, from which he may select one which is closest to the height required. He will therefore remove the block 21 presently located underneath'the frame 24 and place instead the block he has chosen. A difference in height can be taken care of by turning themicrometer knob 36 whereby to either raise or lower the diamond point until the required height has been reached.

The reason why the table bracket 28 of the truing device is shown with the diamond 1 0 1 12 displaced from the bolts 29 is due to the fact that the diamond point should be placed as near to the edge of the magnetic chuck as possible whereby to reduce the distance between this point and the work and shorten the tables length of travel when a dressing of the grinding wheel is required. The clamp 43 which secures the magnetic chuck to the table requires extra space and necessitates therefore placing the brackets mounting surface and its bolt 29 to one side as shown in Fig. 1.

Setting the mechanisms for quantity production The operations required for setting both the surface of the grinding wheel and the point of the diamond in definite relation to the finished height of the work and whereby thereafter quantity work 'for production purposes may be performed, comprise the following steps."

1. Move table 2 with the stop member 44 to the right to a definite stop 45 whereby to locate the diamond point below the grinding wheel.

2. Dress the grinding wheel regardless of dimensions and thereafter bring the table back to the magnetic chuck.

3. Before placing work on chuck measure its thickness. Assuming it is .255" thick and its finished size should be .005 less or .250 thick.

4. The work being held by the chuck is ground down to say .253".

5. Operator will now remember the number he reads on the graduated rim of hand wheel I; say it is zero.

6. He now again moves the table 2 and locates the diamond below the wheel.

' 7. The hand wheel I is turned from its zero position to the graduation marked 3, indicating that the grinding wheel has been lowered .003".

8. The micrometer screw of the dresser is turned until its diamond point touches the sur-' face of the grinding wheel.

Theoretically both the lower grinding surface of the wheel as well as the diamond point are now adapted to operate in a plane situated at substantially the same height as that of the work's surface when finished.

9. To dress the grinding wheel, take on say .002" and turn the handwheel I, to read 5. Move handle for operating table 2 crosswise whereby removing from the grinding wheel .002. After the dressing operation, both the lower grinding surface of the wheel as well as the diamond point will again be situated at substantially the height of the work surface when finished. 1

10. The operator will now remember #5 on the graduated handwheel and by means of the latter will raise the grinding wheel above the work.

11. Knowing that .003" are still to be taken off from the work, the operator now will turn the handwheel to say #7, indicating that he is to take off .002" from its surface.

12. After having reduced the thickness of the work to substantially .251", the work is removed from the chuck and measured as to its correct thickness. If it is found that it measures .251" the handwheel is advanced from #5 to #6, or if it measures more or less than .251", the hand wheel is moved the amount found to be necessary to obtain the finished thickness of .250". After having set handwheel to say #6, it will now be necessary to definitely determine the correct location of the diamond point relative to the finished height of the work. Until now the setting of the point was determined by the method of touchonly.

dressing.

'13. Having determined that the grinding wheel's final setting in relation to the finished height of the work points to #6, on the hand wheels graduations, the operator willnow grind the work on the chuck. Except for small errors that might have crept in when chucking .and measuring the work, he knows that at #6 gradnation, it should now measure correctly within an accuracy of a small fractionof a thousandth of an :inch.

.14. This will therefore enable the operator to finally get the correct position of the diamond point in relation to the finished work, by the expedient of giving the grinding wheel one more #6 to #9 graduation. After the grinding wheel has been dressed, the setting of the diamond 2] in relation to the finished size of the work may now also be considered correct, with the exception perhaps of the above referred to small error that might have crept in.

If after removing the work from the chuck it is found that it measures say thousandth too heavy, that is 0.2505" the operator will turn the knob 36 of the dressing device and lower the diamond by that amount.

If the work measures say thousandth smaller, that is, 0.2495 the diamond point will be raised the referred to amount.

The diamond point is now'in its correct position and the operator is therefore ready to start operation for quantity production.

Operating the mechanism for'quantity production The steps required for grinding successively a large quantity of parts exactly to a uniform height and within an accuracy of a small fraction of one thousandth of an inch is as follows By means of the previous steps described, being required to ascertain the correct setting of the grinding wheel and of the diamond in relation to the finished height of the Work, it was found that,

The latter will be lowered by a certain amount say .003 by turning hand wheel 1 from by the example given the correct location of the rinding wheel was indicated by the #9 graduation on the'hand wheel.

The operator, after placing an unfinished part or parts I0 on the magnetic chuck and after raising the grinding wheel whereby he may start grinding these parts, knows that th lowering of the wheel to #9 graduation during grinding op eration, will have ground the work to the finished height required.

Before however making the last and finishing grind operation he knows that the grinding wheel has to receive a dressing.

Instead of turning the hand wheel to #9 he will therefore go not quite that 'farand turn the wheel to 8 /2 or 8% leaving for the finish grind say /4 thousandth.

Having ground the work to that unfinished height the operator will now move the table tothe right, until block '44 reaches stop and thus 10- cates the diamond point in line with the axis of the grinding wheel. Allowing say 0.002" for dressing the wheel, the operator will now lower this wheel 0.002" plus the A,. thousandth he had allowed for the finish grind. The hand wheel 1 will therefore move to #11 graduation.

The diamond having been previously set for accurate alignment with the #9 graduation, will therefore remove exactly 0.002" during the dressing operation.

After dressing, the operator will return the table with the work "and now take the last finishing "grind of thousandth from its surface.

The work, after it is taken from the chuck, will now measure exactly inside the limits within which the operator was required :to do his work.

Being ready to start with and grind another part or parts, the operator now'kn'ows that for a finish grind of these parts the handwheel will have to be turned to the #11 and not #9 graduations, for the reason that 0.002 had been removed from the grinding wheel during the previous grinding operation,

Before reaching #11 during the new grinding operation, he will again allow say thousandth and set the hand wheel to 10%, so that he may first dress the wheel in the manner previously specified.

Instructing th'e'operator to always allow exactly an equal amount say 0.002" for dressing the grinding wheel, he will therefore know to always add the same amount when setting the handwheel "I.

The steps required for grinding quantities of parts are therefore always the same. 'Ihey'consist in chucking a part or parts, knowing the finished-size munbe r 0n the igraduations of handwheel. Thereafter grinding the surface to nearly finished size required, lowering the grinding wheel for dressing purposes by an amount which is always the same and which comprises the sum of the amount allowed for dressing, say 0.002" as given above, and the amount allowed for the finish grind of the work, say A; thousandth.

The operator will always know the handwheels graduation number for the finished size of the next part or parts, because his directly shown on the rimB as soon as the previously ground part or parts are finished.

It is 'thereforequite obvious that the operations required for grinding quantities ofparts, successively to equal height within any close limit, can now be performed by substantially unskilled hands.

After once setting the grinding machine for quantity work, in the manner described, it is obvious that thereafter the work is reduced to almost automatic operations and may be performed by anyone.

Besides reducing the cost in labor and making skilled .help free for doing other important work, another advantage, although of less importance, is to be found in greatly reducing the wear on micrometer surfaces required for checking .the work.

While heretofore it was necessary to measure with the micrometer each part taken from the chuck, whether it was finished or not, causing the micrometer to rub on the surface, to be measured,

it is evident that within a comparatively short time a micrometer will wear, requiring additional checking as to the micrometer itself.

In the method described, the parts require very little checking. The operator may continue in his work for hours, before the parts need to be checked, and this only when it is believed that the diamond point should have worn a fraction of a thousandth of an inch.

To correct this error, all that is necessary is to turn the knob 36 of the dresser, by the amount measured work should vary relative to its finished size;

Should the diamond be dulled from wear, its shank 20 may be rotated by a small amount "after being made free from screw 22. This, will assure the setting of a sharp cuttingedge or point due to the angular displacement'of the shank relative to the grinding surface of wheel 3.

Having described the invention, it is evident, that various modifications thereof may be apparent to those skilled in the art, without departing from the spirit and scope of the invention, and it is therefore understood that the same is only to be limited by the scope of the prior art and the appended claims.

What we claim is:

1. In grinding mechanisms a grinding wheel and a dressing device adapted for trimming the abrasive material of said wheel, said device comprising a holder, a, sleeve, slidable in said holder and a dressing tool in said sleeve consistingof a shank having a shoulder, adapted for definite location and re-location whenever removed, securing means in said sleeve for said shank adapted to operate in a direction axially to said shank, whereby said shank is bound to always take the exact position it maintained before its removal.

. 2. In grinding mechanisms a grinding wheel and a dressing device adapted for trimming the abrasive. material of said wheel, said device comprising a holder, a sleeve, slidable in said holder and a dressing tool in said sleeve consisting of a shank having a shoulder, adapted for definite location and re-location whenever removed, securing means in said sleeve for said shank adapted to operate in a direction axially to said shank,

whereby said shank is bound to always take the exact position it maintainedbefore its removal and screw mechanisms adapted for moving said sleeve in an axial direction.

3. In grinding mechanisms a grinding wheel and a dressing device adapted for trimming the abrasive material of said wheel, said device comprising a holder, a sleeve, slidable in said holder and a dressing tool in said sleev consisting of a shank having a shoulder, adapted for definite location and re-location whenever removed, securing means in said sleeve for said shank adapted to operate in a direction axially to said shank, whereby. said shank is bound to always take the exact position it maintained before its removal and screw mechanisms adapted for moving said sleeve, the axis of said shank and said securing means havin a common axis with that of said sleeve.

4. In grinding mechanisms, a grinding wheel, a work table, a dressing device fast to said table and adapted for trimming the abrasive material of said wheel, said device comprising a holder having a mounting surface parallel to the working surface of said work table, a sleeve, slidable in said holder and a dressing tool in said sleeve consisting of a shank having a shoulder, adapted for definite location and re-location whenever removed, securing means in said sleeve for said shank, adapted to operate in a direction axially to said shank, whereby said shank is bound to always take the exact position it maintained before its removal. 7

5. In grinding mechanisms a grinding wheel, a work table, a dressing device fast to said table and adapted for trimming the abrasive material of said wheel, said device comprising a holder hav ing'a mounting surface parallel" to the working surface of said work table, a sleeve, slidable in said holder and a dressing tool in said sleeve consisting of a shank having a shoulder, adapted for definite location and relocation whenever removed, securing means in said sleeve for said shank, adapted to operate in a direction axially to said shank, whereby said shank is bOund tO always take the exact position it maintainedbefore its removal and screw mechanisms adapted for moving said sleeve in an axial direction.

6. In grinding mechanisms a grinding wheel and a dressing device adapted for trimming the abrasive material of said wheel, said device comprising a holder, a sleeve, slidable in said holder and a dressing tool in said sleeve consisting of a shank having a shoulder, adapted for definit'elocation and 're-location whenever removed, securing means in said sleeve for said shank adapted to operate in a direction axially to said shank, whereby said shank is bound to always takethe exact position it maintained before its removal and screw mechanisms adapted for movingsaid sleeve in an axial direction, the axis of said sleeve being located'at an angle oblique to the straight cross-sectional contour-line formed on said wheels surface during dressing operation.

"7. In grinding mechanisms a grinding wheel and a dressing device adapted for trimming the abrasive material of said wheel, said device comprising a holder, a sleeve, slidable in said holder and a dressing tool in said sleeve consisting of a shank having a shoulder, adapted for definite location and re-location whenever removed 'securing means in said sleeve for said shank adapted to operate in a direction axially to said shank, whereby said shank is bound to always take the exact position it maintained before its removal, screw mechanisms adapted for moving said sleeve in an axial direction, indicating means comprising graduations and forming part of said screw mechanisms, the axis of said sleeve being located at an angle oblique to the straight cross-sectional contour-line formed on said wheels surface during dressing operation, the magnitude of the pitch of the thread of said screw mechanisms and the width of the graduations of said screw mechanisms having a definite relation to the angle of said sleeve.

8. In grinding mechanisms, a work table, a grinding wheel above said table and means adapted for changing the height between said table and said wheel, graduations forming part of said means, being adapted to indicate a change in height between said table and said wheel, a dress ing device adapted for trimming the abrasive material of said wheel, said device comprising a holder, a sleeve slidable in said holder, and a dressing tool in said sleeve consisting of a shank having a shoulder, adapted for definite location and re-location whenever removed, securing means in said sleeve for said shank adapted to operate in a direction axially to said shank, whereby said shank is bound to always take the exact position it maintained before its removal and screw mechanisms adapted for moving said sleeve in an axial direction, indicating means comprising graduations and forming part of said screw mechanisms, said graduations comprising units of measure identical in character to the graduations of said changing means, the axis of said sleeve being located at an angle oblique to the straight cross-sectional contour-line formed on said wheels surface during dressing operation, the magnitude of the pitch of the thread of said screw mechanism and the width of the graduations of said screw mechanisms having a definite relation to the angle of said sleeve.

FRANK SWENSON. ERIK IVER ERIKSON. 

